Ceramic matrix composite (CMC) is a useful material for making components used in many applications including aircraft and automobiles. Moreover, when the CMC is reinforced with fiber the resulting material can be used to make components that are resistant to extremely high temperatures and surprisingly strong and durable. For example, fiber-reinforced CMC can be used to make components such as piston rings, catalytic converters, exhaust manifolds, brake rotors and brake pads.
A CMC component is typically manufactured by mixing a resin with fibers and filler powders to form a mixture. This mixture is then loaded into a mold in the shape of the desired component. Next, the mixture is cured by raising the temperature of the mold and the mixture to the cure temperature of the resin. Curing occurs when the mixture has set enough such that the component is formed.
The newly formed component is then ejected from the mold. At this stage the component is in a "green-state." This means that it has not been pyrolized, or raised to a high enough temperature whereby a ceramic is formed. Thus, in its "green-state" the component is a polymer composite that has structural integrity and can be handled but still needs to undergo pyrolysis before the component can be used.
Generally, this fabrication process takes a substantial amount of time. This is partly because resins, especially polymer-derived ceramic precursor resins, tend to cure rapidly when raised to their cure temperature. Consequently, the mold and the mixture must be cool when the mixture is loaded into the mold to ensure that the resin does not cure prior to closing the mold. Instead, the cool mold and the mixture must be heated to the cure temperature. Typically, this heating takes in excess of one hour due to the thermal mass of the forming tool.
One problem with this manufacturing process for CMC components is that it takes a substantial amount of time to manufacture a CMC component. This relatively long manufacturing time of CMC components is one reason why CMC components have difficulty competing in the marketplace with similar components made from traditional materials. This is despite the fact that CMC components are generally lighter, more durable and more efficient traditional materials in widespread use. For example, a traditional brake pad can be manufactured in a matter of seconds. Conversely, a CMC brake pad, which is more resistant to high temperatures and more durable, takes in excess of one hour to manufacture.
Another problem with the manufacturing process of CMC components is that the large discrepancy between manufacturing times has the effect of drastically increasing the cost of a CMC brake pad compared to a traditional brake pad. This, in turn, has hindered the widespread use of CMC components in favor of components made from traditional materials.
Therefore, what is needed is a method of rapidly manufacturing a CMC component that yields a CMC component that retains its resistance to high temperature, strength and durability. Moreover, this method of rapid manufacture would in turn decrease the production costs of the CMC component and would allow the CMC component to compete in the marketplace with similar components made from traditional materials. Furthermore, what is also needed is a method for rapidly manufacturing CMC components that yields a mixture which has a long shelf life. This would permit preparation of the mixture well ahead of production and alleviate slowdowns in manufacturing.
Whatever the merits of the above-mentioned methods of manufacturing CMC components, they do not achieve the benefits of the present invention.